1. Field of the Invention
The present invention is concerned with a process for preparing 17.beta.-carboxy-4-androsten-3-ones.
2. Description of the Prior Art
Heretofore, 17.beta.-carboxy-4-androsten-3-ones have been prepared from the corresponding 17.beta.-(1-ketoethyl)-5-androsten-3-ols by means of the haloform reaction in which cleavage was brought about by addition of dilute sodium hydroxide to the starting material, followed by a slight excess of iodine in potassium iodide solution, warming, and addition of water. However, this reaction has been found to give poor yields and to require the use of expensive reagents. By contrast, the method of the present invention is characterized by rapid and high yield of product, and a more efficient use of expensive reagents.
It has also been known to prepare 3.beta.-hydroxy-5-androstene-17-carboxylic acid by treating 3.beta.-hydroxy-5-pregnene-20-one with iodine and pyridine and carrying out alkaline decomposition of the 21-pyridinium intermediate. See King, L. carroll, J. Am. Chem. Soc., Vol. 66, p. 1612 (1944). However the method of the present invention permits preparation of the methyl carboxylate ester directly, rather than the acid which is formed in the King method. The ester is a blocking group which permits subsequent modifications to the A and B rings.